This invention relates to a detent mechanism for a pressure control valve, and more particularly to a detent mechanism for a pressure control valve wherein a control lever is provided with pressing sections and also provided at a portion thereof below each of the pressing sections with a push rod, so that pivotal movement of the control lever may cause each of the pressing sections to force or push the push rod. The amount or extent of movement of each of spools may be determined depending on the amount or extent of forcing of the pressing section or the amount or extent of pivotal movement of the control lever, resulting in pressure on a secondary side which acts on the spool being controlled.
A conventional detent mechanism for a pressure control valve of such type which has been extensively used in the art is typically disclosed in Japanese Patent Application Laying-Open Publication No. 101175/1982, the disclosure of which is incorporated by reference. The conventional detent mechanism is constructed in such a manner as shown in FIG. 1. More particularly, it includes a control lever 1 which is provided with at least a pair of forcing sections 2 and 3. The forcing sections 2 and 3 are abutted against one end of rods 4 and 5 formed of a nonmagnetic material, respectively. The following description will be made in connection with the rod 4 because both rods are constructed in substantially the same manner.
The rod 4 is arranged in a manner to be inserted through a solenoid 6 and has a magnetic cap 7 fixed at the other end or a distal end thereof. The detent mechanism also includes a push rod 8 which is abutted at a distal end thereof against each of the magnetic caps 7 and provided with a guide member 9. Between the magnetic cap 7 and the guide member 9 of the push rod 8 is interposed a spring 10. Below the guide member 9 is arranged a spool (not shown), on which a pressure control spring acts. The pressure control spring is adapted to exhibit elastic force controlled depending on the extent of operation of the control lever 1.
When the control lever 1 is pivotally moved in a clockwise direction in FIG. 1, the rod 5 is pushed down by the forcing section 3 of the lever 1 and the rod 4 and magnetic cap 7 are raised by the action of the spring 10.
When the rod 5 is pushed down as described above, the spool positioned below the rod 5 is changed over and the force of the pressure control spring is controlled depending on the amount or extent of changing-over of the spool or the extent of operation of the control lever 1.
When the force of the pressure control spring is thus controlled, the controlled force causes the spool to be actuated to keep pressure on a secondary side thereof below a predetermined value.
When the control lever 1 is inclined to a maximum extent in the clockwise direction, the magnetic cap 7 is sucked on the solenoid 6, the spool as well as the control lever 1 is held at its changing-over position to keep force on the secondary side at a pressure value predetermined depending on the force of the pressure control spring.
Thus, such a conventional detent mechanism as described above is so constructed that the solenoid 6 is provided on an axis of the push rod 8. Such construction causes the additional rods 4 and 5 to be required to force the push rod 8 and the solenoids and rods to be received in a casing C, resulting in a structure of the detent mechanism and therefore the pressure control valve being highly complicated.
Also, arrangement of the solenoid 6 through the rod 4 fails to provide lubrication sufficient to carry out smooth sliding between the solenoid 6 and the rod 4, resulting in galling.
Further, holding of the magnetic cap 7 on the solenoid 6 by suction causes the directions of hydraulic reaction force and suction force to be opposite to each other. Accordingly, in order to keep the magnetic cap 7 on the solenoid 6 by suction, it is required to cause the suction force to be larger than the hydraulic reaction force. This causes the solenoid 6 to be large-sized, to thereby lead to further complication of the structure.